From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,63e8a95e8331225 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-04-22 14:15:12 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!newsgate.duke.edu!newsfeed!nntp.TheWorld.com!not-for-mail From: Robert A Duff Newsgroups: comp.lang.ada Subject: Re: Partial Hardware Protection for Buffer Overrun Exploits Date: 22 Apr 2003 17:15:09 -0400 Organization: The World Public Access UNIX, Brookline, MA Message-ID: References: <3EA41F8E.8030305@cogeco.ca> NNTP-Posting-Host: shell01.theworld.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: pcls4.std.com 1051046109 8824 199.172.62.241 (22 Apr 2003 21:15:09 GMT) X-Complaints-To: abuse@TheWorld.com NNTP-Posting-Date: Tue, 22 Apr 2003 21:15:09 +0000 (UTC) User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 Xref: archiver1.google.com comp.lang.ada:36370 Date: 2003-04-22T17:15:09-04:00 List-Id: "Frank J. Lhota" writes: > The first Intel chips that supported protected mode were the rarely-used > 80186 The 80186 did not support protected mode. It was practically identical in architecture to an 8086 or 8088. The 80186 had a small number of additional instructions -- e.g., pushall for pushing all registers, I think (for some definition of "all"). It was used in mainly in embedded systems, I believe. >... and the 80286 chips that powered the IBM PC/AT. These early chips > supported a command for transitioning from real to protected mode, but no > simple command for transitioning back to real mode. This is what earned > these chips the "brain dead" assessment from Gates. Well it *was* pretty brain dead, for this and other reasons. >...The lack of a quick way > to get back to real mode was a problem for MS, who wanted protected-mode > extensions to DOS (such as Windows 3.x and OS/2 1.x) to be able to use the > real mode I/O kernel of DOS. Their solution was the "mini-reboot" of the > CPU, for which they paid a performance penalty. > > All of these problems went away with the next generation of Intel chips (the > 80386 and beyond), which can quickly toggle between real and protected > modes. Right. In fact, the 80386 introduced "virtual 8086 mode", which allows multiple real-mode virtual 8086 machines running on the same machine. - Bob